We pay bills etc proportionately according to the income we each have, which in practice means DH pays a lot more than me because I am retired and my income is much less, while he is still working.  

We have a joint account and each have a separate account. DH makes about 24k more than I do but he puts about $100 less into the joint account because of child support, health insurance, and a loan he's paying. From that account we buy all groceries and other joint expenses - mortgage, utilities, car stuff, house stuff, etc. Maybe you two should do something like that.- but you should put in less than he does. Except after CS and extras he's not making much more than you.
 

The OP has a child that lives in the home full time.  Should her husband be expected to help support her "OOPS child"?

If your son wasn't involved, I would say your husband should be contributing more.  But your child changes things a bit.  You and your son's father should be covering all of your son's expenses.   Your son is in the home full time.  Aren't you the poster who said your SKs only come one weekend a month and on holidays?  If so, paying based solely on income isn't fair.  

Just as you shouldn't be expected to subsidize his kids, he should be tasked with subsidizing yours.

If I were in your shoes, I would ask my husband to cover all expenses for a short amount of time.  During that time I would return to school full-time to earn whatever degrees I needed to increase my earning potential.

Together, you make $132,000. Of that, 30% is your income. Therefore, you pay 30% of the household expenses. If you want to take out CS, which I advise against, it's about 40%.

I'm assuming that since your DH makes more than you, you have a higher standard of living than you would if you were on your own. It's not fair to expect you to pay more than or equal to what your DH would for a standard of living that you cannot obtain on your own.

I like having a "yours, mine, and ours" system for money. "Ours" are any bills and savings we need for things that we mutually benefit from. That would include rent/mortgage, utilities, internet, cell phones on a shared plan, shared vehicles if you co-own them, shared credit card debt, and emergency household savings to pay for 3-6 months worth of JOINT expenses in the event one or both of you find yourselves jobless. Other joint expenses or savings can be negotiated here, such as a vacation or home remodeling fund.

Then, any money leftover is "yours/mine". That's what is used to pay individual debts or bills for items you SOLELY own or use, play money, retirement, personal savings, and, yes, CS and other kid-related expenses.

If your DH doesn't have the funds to pay for HIS portion of household expenses, then you two need to discuss a lower standard of living or he needs to consider a second job. He could also consider looking for a reduction in CS since he seems to be being taken to the cleaners (unless he has a gaggle of kids) since he's paying more than 30% of his gross income plus 75% of medical expenses. A downward adjustment might be called for.

If he wants a better standard of living for his kids in his household, then HE has to provide it. It's not your responsibility to supplement his shortfalls.

ETA: This does get slightly more complicated if you have a child in the home FT that isn't your DH's. In that case, you need to adjust your income based on the amount of CS you SHOULD be receiving. If your ex isn't paying CS, it's not your DH's responsibility to make up that shortfall for your kid. That means you may need to take your ex to court or get a second job to make up that lost income for your son.

Don't pay for more than your fair share. If he can't afford his share then it's time to downsize. 

He should look into getting his child support order(s) reviewed. That is a crazy amount to pay.